1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a backlight module that enhances brightness of light guide plate.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal panel and a backlight module. The operation principle of the liquid crystal panel is that liquid crystal molecules are interposed between two parallel glass substrates and a plurality of vertical and horizontal fine electrical wires is arranged between the two glass substrates, whereby the liquid crystal molecules are controlled to change direction by application of electricity in order to refract light emitting from the backlight module for generating images. Since the liquid crystal panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of an LCD. The backlight module can be classified in two types, namely side-edge backlight module and direct backlight module, according to the position where light gets incident. The direct backlight module arranges a light source, such as a cold cathode fluorescent lamp (CCFL) or a light-emitting diode (LED) at the back side of the liquid crystal panel to form a planar light source that directly provides lighting to the liquid crystal panel. The side-edge backlight module arranges a backlight source of LED light bar at an edge of a backplane to be located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face formed at one side of the light guide plate and is projected out through a light emergence face of the light guide plate, after being reflected and diffused, to transmit through an optic film assembly thereby forming a planar light source for the liquid crystal panel.
Referring to FIG. 1, in a side-edge backlight module, a gap is present invention between a mold frame and a light guide plate/optic films. In normal operations, the mold usually undergoes deformation caused by heating or other factors or the gap might be of an excessive size, whereby light from an LED light source, upon incident onto the mold frame, may project outward through such a gap, forming a bright line and thus leading to around 3% loss of brightness of the light emitting from the LED light source. Referring to FIG. 2, this situation is caused by a component of the light from the LED light source 200 getting incident to the mold frame 600. To solve such a problem, the technical solution that is conventionally taken is arranging a reflective layer 700 on the mold frame 600 at the site corresponding to the LED light source 200, the light guide plate 300, and optic film 500 in order to reflect back the light incident to the mold frame 600. However, there is still a fraction of the light that is reflected toward the gap between the light guide plate 300 and the mold frame 600 to get out and form a bright line, leading to a loss of brightness of the light emitting from the LED light source 200. With the development that uses an LED light bar to serve as the backlight module, a backlight module with a slim frame (less than 8.0 mm) is now becoming the new trend of the future development. However, in such a slim frame backlight module, the problem gets severe and becomes an issue that must be addressed immediately.